However, this assertion is somewhat difficult to prove, using the actual script of Frontios itself. In trying to explain where the Frontios colony of humans came from, the Fifth Doctor stops himself at the word "great", in an apparent attempt to spare Tegan's feelings. But she is insistent:

Tegan: In the great what, Doctor?

Doctor All civilisations have their ups and downs.

Turlough: (reading from TARDIS computer) "Fleeing from the imminence of a catastrophic collision with the sun, a group of refugees from the doomed planet Earth ..."

So, while, the Fifth Doctor comes awfully close to saying the words "Great Catastrophe" in Frontios, he doesn't quite make it. Gatiss is therefore connecting some dots that the script doesn't. The connection is also difficult to make since Frontios is usually considered to take place in the far future, well beyond the 38th century.